chrome.runtime.onInstalled.addListener(function() {
  chrome.storage.sync.set({ color: '#3aa757' }, function() {
      console.log("The color is green.");
  });
  chrome.declarativeContent.onPageChanged.removeRules(undefined, function() {
    chrome.declarativeContent.onPageChanged.addRules([{
        conditions: [new chrome.declarativeContent.PageStateMatcher({
            pageUrl: { hostEquals: 'i.mooc.chaoxing.com' },
        })],
        actions: [new chrome.declarativeContent.ShowPageAction()]
    }]);
  });
});